Ireland flanker Stephen Ferris has been ruled out of the remainder of the Six Nations with a knee injury.

The Ulster blindside has been out of action since re-injuring the joint during his side's victory over Aironi at the end of January.

Since then his place in the Ireland back-row has gone to Munster's Denis Leamy and Leinster's
Sean O'Brien for Championship clashes with Italy, France and Scotland, with ties against Wales and England to follow in March.

Ferris' focus is now on regaining full fitness in time for Ulster's Heineken Cup quarter-final against Northampton at Stadium:mk on April 10.

"I think it's fair to say that we can rule Stephen Ferris out of the rest of the Six Nations so he is gone for those two games," Ireland team manager Paul McNaughton told The Irish Times.

"He is down for a consultant's visit to London this weekend and they will know more about that, but it is too early to write him out of the Heineken Cup game at this stage."

An injury cloud also hangs over scrum-half Tomas O'Leary, who missed the victory over Scotland with a back problem, but McNaughton believes that the Munster No.9 could yet play a role in the tournament.

"Tomás O'Leary is continuing rehab with his back and we are not ruling him out of any games at this stage," he said.